This invention relates to an attachment for diagnostic ultrasound probe and, more particularly, to an attachment which is to be mounted in an ultrasound probe when examining an organ present in the neighborhood of the surface of the body.
The ultrasound probe has a transducer array having a plurality of transducer elements aligned in one direction. An ultrasound beam is emitted from the transducer elements to the body along a scanning plane. Ultrasound beam reflected by the interior of the body is received by the transducer elements. The body thus is scanned by the ultrasound beam along the scanning plane. The received ultrasound beam is converted into an electric signal so that a tomographic image of the body is displayed on a cathode-ray tube.
When an organ present in the neighborhood of the surface of the body is examined, an attachment accommodating an acoustic medium is mounted in an ultrasound probe. FIG. 1 shows this attachment. Attachment 2 comprises box-like reservoir section 3 accommodating an acoustic medium and mounting section 4 for mounting reservoir section 3 in ultrasonic probe 1. FIG. 2 schematically shows reservoir section 3. Reservoir section 3 includes auxiliary membrane 5 which is held in contact with ultrasound probe 1 and can transmit ultrasound beam, and contact membrane 6 which is disposed such that it faces auxiliary membrane 5, held in contact with the body and can transmit ultrasound beam. Reservoir section has a pair of side walls 8 which extend at right angles to scanning plane 7 and have one end connected to contact member 6, and a pair of top walls 9 which extend at right angles to scanning plane 7 and substantially parallel to contact membrane 6 and have one end connected to auxiliary membrane 5.
A major part of the ultrasound beam emitted from ultrasound probe 1 is transmitted through auxiliary membrane 5 and contact membrane 6, to be transferred to the body. However, the remaining part of the ultrasound beam is reflected by the inner surface of contact membrane 6, to be transferred to side walls 8 for multiplex reflection. More specifically, as shown by arrows in FIGS. 1 and 2, the ultrasound beam is transferred along first path 11 in scanning plane 7. Side walls 8 extend perpendicular to scanning plane 7. A part of the ultrasound beam reflected by the inner surface of side walls 8 is returned along first path 11 in scanning plane 7 to contact membrane 7, to be reflected by the inner surface thereof and returned to ultrasound probe 1. The returned ultrasound beam contains data concerning side walls 8. Thus, an image of side walls 8 is displayed on cathode-ray tube 28 as artifact, as shown by broken lines in FIG. 14. For this reason, it is liable that accurate diagnosis is prevented.
FIGS. 3 and 4 show an attachment, in which the distance between the lower ends of pair side walls 8 is greater than the distance between the upper ends of the side walls. Again in this attachment, side walls 8 extend at right angles to scanning plane 7, so that a part of the ultrasound beam reflected by the inner surfaces of side walls 8 is returned along first path 11 to contact membrane 8 and thence returned to ultrasound probe 1. For this reason, it is liable that an image of side walls 8 is displayed on cathode-ray tube.
Further, a part of the ultrasound beam emitted from ultrasound probe 1 and reflected by the inner surface of contact membrane 6 is liable to be transferred to top walls 9 for multiplex reflection. More specifically, as shown by arrows in FIGS. 1 to 4, the ultrasound beam reflected by the inner surface of contact membrane 6 is transferred along second path 12 in scanning plane 7. Top walls 9 extend substantially parallel to contact membrane 6. A part of the ultrasound beam reflected by the inner surface of top walls 9 is returned along second path 12 in scanning plane 7 to contact membrane 6, to be reflected by the inner surface thereof and returned to ultrasound probe 1. For this reason, like the case described above, the returned ultrasound beam has data concerning top walls 9. An image of top walls 9 thus is displayed as artifact on the cathode-ray tube.
Further, as is described above, reservoir section 3 accommodates an acoustic medium. This acoustic medium is, for example, water or colloidal material. When the acoustic medium is poured into reservoir section 3, air is liable to enter reservoir section 3. There is a possibility that the organic body is scanned by the ultrasound probe while the probe is disposed perpendicular to the body. At this time, auxiliary membrane 5 extends horizontally. For this reason, it is liable that air, i.e., air bubbles, is retained on the lower surface of auxiliary membrane 5, as shown in FIGS. 1 and 3. In this case, the ultrasound beam is blocked by air bubbles, resulting in deterioration of the quality of the tomographic image displayed on the cathode-ray tube. In such a case, air is expelled as much as possible by means of frequently replenishing reservoir section 3 with the acoustic medium. Even with this means, however, it is difficult to perfectly expel air from reservoir section 3.